1. Field of the Invention
The present invention relates to a method for producing a sucrose fatty acid ester (hereinafter referred to simply as SE).
2. Discussion of Background
SE is widely used as a highly safe nonionic surfactant having both an excellent surface activating ability and a good biodegradation property for food products as well as for cosmetics, pharmaceuticals, cleaning agents and feed stuff.
As a method for producing SE, a method is known which comprises subjecting sucrose and a lower alkyl ester of fatty acid to an ester exchange reaction in an organic solvent such as N,N-dimethylformamide or dimethylsulfoxide in the presence of an alkali catalyst (JP-B-35-13102). The obtained reaction mixture contains the solvent, unreacted sucrose and the alkali catalyst, in addition to SE. To separate SE from this mixture, it is common to employ a method wherein upon deactivating the catalyst by an addition of an acid, the solvent is partially recovered, then by liquid-liquid extraction treatment with an organic solvent and water, SE is distributed to the organic solvent phase, and the unreacted sucrose and the rest of the solvent are distributed to the aqueous phase, and from the obtained organic solvent phase, the organic solvent is distilled off to separate and purify SE (for example, JP-B-48-21927, JP-B-48-35049, JP-A-50-29417, JP-A-50-130712). On the other hand, the unreacted sucrose and the reaction solvent recovered in the aqueous phase will be reused for the next reaction after removing water by distillation.
SE obtained by the above method usually contains a few % in total of a free fatty acid and an alkali metal salt of fatty acid (hereinafter referred to simply as a soap). These components have frequently given various influences over the physical properties or the function of SE, although their upper limits are stipulated in the regulations for food additives. For example, the free fatty acid remarkably lowers the water solubility of SE, and when SE has been used for oil-in-water type emulsification or dispersion solubilization, variation in the acid value has been a serious problem for the quality control.